1. Field of the Invention
The present invention relates to a bearing assembly and a crown-shaped retainer for use in a rolling bearing assembly and, more particularly, to the structure of a retainer capable of providing a low torque.
2. Description of Related Art
Most of ball bearing assemblies currently available are used in a condition with a grease filled therein as a lubricating agent and sealed by a seal or a shield. The bearing assembly utilizing the grease has some advantages in that as compared with the lubrication with oil, no oil supply system is needed, and is hence maintenance free. In the bearing assembly, not only does a rotating torque, that is, a resistance to rotation occur, but also influences brought about by the friction present between rolling elements and a retainer and agitation and viscosity of a lubricating agent tend to affect the operability of the bearing assembly. Where the lubrication with a grease takes place in the bearing assembly, an agitating resistance, with which balls and/or a retainer agitate the grease, and an shearing resistance, with which the grease is sheared between the retainer and sealing members, form a torque of the bearing assembly.
In the bearing assembly of a kind that is lubricated with a grease, as a related art technique designed to lower the rotating torque, the disclosure has been made that depending on the composition of the grease used to lubricate, the rotating torque of the bearing assembly tends to be lowered even at a low temperature (such as disclosed in, for example, the patent document 1 listed below). Also, as another related art technique designed to achieve a low torque in the bearing assembly, the disclosure has been made that a minimum required amount of a lubricating agent is seized in between inner peripheral faces of retainer pockets and rolling surfaces of the rolling elements to thereby reduce retainer noses and the rotating torque (such as disclosed in, for example, the patent document 2 listed below). As a further related art technique designed to achieve a low torque with a retainer, the disclosure has been made that when rolling elements collide against pockets, a groove having a cushioning function is provided between the neighboring retainer pockets (such as disclosed in, for example, the patent document 3 listed below).
As a yet other related art technique designed to achieve a low torque in the bearing assembly, the disclosure has been made that the composition of a bearing sealing portion and the shape are modified (such as disclosed in, for example, the patent document 4 listed below).